Water...a necessity of life.
But let's use our common sense about it.
Adults need to drink at least 8 ounces of water a day.
This one may be a good rule of thumb, but it actually defies logic. Does a 5-foot woman need as much water as a 6-foot man?
Doesn't it depend on diet also? Someone who eats a lot of soup, fruit, and vegetables, is not going to need as much water as someone who eats a meat and starch diet, because they get it naturally.
Soda water (soft drinks, cola, pop, whatever you call it in your area of the world) dehydrates you more than the water in it hydrates you.
Think about it. Yes, the small amounts of carbon and caffeine may be a tiny bit dehydrating, but there is so much higher percentage of water that it does not dehydrate you. It may not hydrate you as well as plain water, but it does not make you dehydrated.
By the time you feel thirsty, you are already dehydrated.
Well, yeah, but is it a bad thing? Nature has wonderful ways to tell you that your body is out of balance, and thirst is one of them. You start to feel a bit thirsty, so you get a drink. Voila, balance restored! I am not a doctor, but I think if you are force-feeding yourself water, you are just as likely, if not more so, to get out of balance. You may be flushing out nutrients and things that you need.
Unsupported statement with unsupported reasoning:
Drinking water during meals interferes with digestion.
My opinion: It waters down the stomach acids, but they rebound quickly. Meanwhile, the extra fluid helps the food keep moving smoothly through your system, possibly preventing constipation and its related problems. If you shouldn't drink water with meals, then people shouldn't eat soup either.
However, if I drink a lot of water on top of a heavy meal, it may make me burp a bit of it up because my stomach ran out of room. When I drink water, or any other drink, along with a meal, it doesn't bother me at all.
Drinking water at certain times of the day will cure or prevent diseases.
Water is water. Why should the time of day matter? Your organs sit there during the night and do their jobs while you rest. They don't need "wakening" or "settling down" for the night. They do need water, but they don't have a clock ticking in there with little alarms going off to give you a disease if you happen to miss a watering.
Drinking cold water causes cancer.
No, it just refreshes you. Your body has marvelous mechanisms for regulating temperature. If cold water caused cancer, then so would anything else cold, including fruit salad and ice cream. They may have their own problems, but cancer from cold is not one of them.
What I think about water: it's a marvelous thing. I feel a bit droopy or get a slight headache and a glass of water can perk me right up. Ice water is nice on occasion, especially if your water doesn't taste good, because the cold numbs the taste buds a bit. Some things just taste better cold, like soda and root beer floats! But if I'm hungry, a glass of water doesn't make me less hungry. It does make me less thirsty.
Snopes.com: Water Works
Snopes.com: Water Weal
Snopes.com: Cold Comford